Application of direct calculation methods to the determination of wave external loads for assessing the strength of the ship hull

An approach to the determination of wave loads using direct hydrodynamic calculations for their subsequent use in finite element models of the hull structure is considered. A number of hydrodynamic calculations based on solving the equations of the linear theory of ship pitching by the linear method have been carried out. The results of calculations in the form of pressures and pitching parameters are compared with the values obtained by the formulas of classification societies. With the help of the apparatus for converting the random input process of excitement into the output process of response, their short-term and long-term characteristics are constructed. From the received wave responses, when assigning the dominant, even wave cases are formed. The set of dominant responses is formed on the basis of general principles and accumulated experience in analyzing the strength of the vessel, presented in the rules of various classification societies. For each wave case, the corresponding position of the vessel on a conditional equivalent wave is selected from the rules, for which the accompanying components of the wave action are determined. This approach allows the calculation models of the FEM to simultaneously take into account the entire system of external actions responsible for general and local strength. Comparison of the pressure plots obtained by the direct method in cross-sections demonstrates qualitative convergence with the pressure plots laid down in the calculation formulas of the rules of classification societies.

Automated summary

This approach proposes a method for determining wave loads using direct hydrodynamic calculations and applying them to finite element models of the hull structure. By comparing the calculations with classification society formulas and using a random input excitation conversion device, short-term and long-term characteristics are constructed. The approach allows for the consideration of all external actions responsible for the overall and local strength simultaneously.